The present invention relates to a raster scan unit for providing a flexible, controllable raster generator for a plan view display.
Most graphic display devices use a TV-scanning technique wherein the electron beam of a picture tube sequentially scans a screen from the upper to lower ends in accordance with a predetermined scanning pattern in order to simplify the deflection operation of the scanning beam of the tube. In order to provide greater versatility to graphic display devices, various modifications to raster patterns have been made. For example, in U.S. Pat. No. 3,988,728, entitled "Graphic Display Device" which issued Oct. 26, 1976, to Inoue et al, a pattern shifting device is described for shifting, on demand and in an amount selected by an external computer, the display of a pattern in a direction transverse to the direction of raster scanning.